Is it the black, or the clear that's scummy?

[nicholebeth]

I tried to make several encased black beads last night, and more often than not, as I was getting the clear on, a gray scum appeared over parts of the black. Is it the glass, or a propane/oxygen balance thing? I'd show a pic, but I threw them in the water jar as it happened, so they no longer exist. I'm not sure if its effetre or vetrofond black (they aren't labeled!), and I was using lauscha clear. I've never seen Lauscha do this on any other color.

[Kikki]

I've had it happen too and I've heard that this can happen if the black is too cool when you put the clear on.